Field of the Invention
The present invention, relates to a method for producing a toner that is suitable for an electrophotographic method, an electrostatic recording method, and a magnetic recording method.
Description of the Related Art
In recent years, the increased variety of intended uses and usage environments of linage forming apparatuses, such as copiers and printers, created a demand for additional energy saving. Energy saving improvements resulting from toner are primarily associated with toners with a further improved low-temperature fixability.
As a means tor creating such toners, the use of crystalline polyesters which rapidly compatibilize with the binder resin of the toner and enhance melting deformation of the toner has been actively studied in recent years.
Crystalline polyesters which are highly effective in improving low-temperature fixability are capable of easily compatibilizing with the binder resin in the vicinity of the melting point of the crystalline polyesters, and the toner tends to melt and deform rapidly at the time of fixing. This is why the low-temperature mixability of the toner is increased as a result of using the crystalline polyester.
Further, additional improvement in the fixing ability can be expected from the usage of a release agent, such as a wax, which can impart the toner with releasability with respect to a fixing unit.
However, since the crystalline polyesters are capable of easily compatibilizing with the binder resin, the crystalline polyester becomes easily present on the toner surface, thereby reducing the charging performance of the toner. An additional problem is that where the toner is stored in a severe environment with a temperature and humidity higher than usual, the polyester resin which has compatilibized with the binder resin is annealed by this temperature and crystallizes. The abovementioned environment will be referred to as “severe environment”, and allowing the toner to stand in such environment will be referred to as “storage in the severe environment”. Where such problem occurs, the surface composition of the toner-changes in the course of storage in the severe environment, and performance thereof is greatly degraded, for example, by occurrence of fogging.
Reducing the amount of the polyester resin compatibilized with the resin binder has been investigated to resolve this problem. Reducing the compatibilized amount means that a state with a high degree of crystallinity of the crystalline polyester is achieved. In particular, methods for producing toners that are aimed at the crystallization of the crystalline polyesters have been studied.
In Japanese Patent Application Publication No. 2010-145550, the degree of crystallinity of a crystalline polyester is increased by controlling the cooling rate. In Japanese Patent Application Publication No. 2014-211632, an annealing treatment step is provided in the cooling process to increase the degree of crystallinity of a crystalline polyester.
However, in terms of the decrease in charging performance caused by the presence of a crystalline polyester on the toner surface, and the resistance to storage in the severe environment in which a variety of material flows are assumed to occur, there is still room for improvement with respect to the abovementioned patent literature. Thus, there is room for investigating the techniques for encapsulating a crystalline polyester in a state with a high degree of crystallinity in a toner.